The present invention relates to a new and improved method for altering the dimensions of a cast strand or casting during continuous casting operations, while the pour or teeming operation is in progress, wherein at least one movable mold wall is moved by means of two displacement devices arranged in tandom in the direction of strand travel, about a pivot axis extending transversely with respect to the lengthwise axis of the strand and parallel to the mold wall and transverse to the strand lengthwise axis. The invention also relates to novel apparatus for the performance of the aforementioned method.
During the continuous casting of strands, especially during the continuous casting of steel, there is already known in this technology to employ plate molds having movable walls for changing the taper of the hollow mold compartment between the narrow sides of the mold during such time as the continuous casting operation is in progress, i.e. during the pouring or teeming operation.
There is also known to the art a method for increasing the dimensions of a continuously cast strand, during the continuous casting operation, i.e. without interrupting the infeed of steel. Here, at least one of both movable transverse walls or short sides of plate molds are moved by means of two spindles arranged in tandem or behind one another in the direction of strand travel. The narrow or short side of the mold is pivoted during a first step, thereafter during a second step is shifted parallel to itself transversely with respect to the lengthwise axis of the continuously cast strand, and during a third step is again pivoted back into a position corresponding to the desired casting taper. During the first step the narrow side is moved about a pivot axis which coincides with the outlet edge of the narrow side of the continuous casting mold. During the third step the pivot axis is located at the region of the bath level or meniscus or coincides with the inlet edge of the narrow side of the continuous casting mold.
However, there is also known to the art a method wherein while the casting or teeming operation is in progress, the width of a slab casting is decreased. Also with this method there are carried out the three aforementioned steps, to wit, pivoting, parallel displacement, pivoting back of the narrow or short side of the mold.
With the heretofore known methods there are formed during the pivotal movement air gaps between the strand shell or skin and the mold wall and/or impermissible deformations at the still thin strand shell with the corresponding friction and mold wear. These conditions therefore require extremely low pivoting speeds of the mold wall if the risk of metal break-out is to be maintained small. Small pivoting speeds result in small adjustment speeds and, apart from a low casting output, additionally produce long, conical transition pieces between the old strand format or sectional shape and the new strand format. These are undesired because they require correction by flame cutting operations or the like.